I'm going crazy figuring out why my car is so weak!
 

My mods are:

Vortech with 2.87 pulley
DW 550cc injectors
AAM Stage 1 Fuel Return
Walbro fuel pump
Skunk2 Plenum Spacer
Megan Racing longtube headers
Ebay "Nismo" replica exhaust with cutout.

My car is a 2003 G35 5AT w/ 80K miles ( 5K on the Vortech ) and it has 20" wheels ( rear wheel + tires weigh over 60lbs ).

Yesterday I went to the dyno and tuned my new setup ( the 2.87 pulley and AAM fuel return ). The tune came out beautiful, AF was flat at 11.4/11.5 and timing was in the 18-19* range with no knock. Boost would go to 11psi at redline.

The problem is that I only put down 367whp on a DJ. I don't have the graph with me but it was SUPER smooth ( even with smoothing at 0 ) and was very straight ( no dips and no fall off ). Just imagine the most beautiful Vortech dyno graph...at only 367whp.:dunno:

My car has absolutely no blow by ( very little at WOT and no oil is coming out ) and runs and pulls great...just underpowered. Could my engine be bad without it showing signs of being bad?

What could be wrong? Some people say my 20's are killing me but could I lose 40-60whp from my 20's? I need ideas?

Also, on a single 3rd gear pull my IAT went from 110* to 140*...would it be safe to say my intercooler is not doing it's job well?

Well wheels/tires that heavy are certainly stealing power getting to the ground. How much is hard to say. But I know it can be a lot, especially if they are that heavy.

Anyone have wheels you can borrow to try with something lighter?

Tom

I'm looking into it to see if I can swap some wheels at the dyno. But could I lose THAT much power?

367whp is embarrassing. Maybe something is broken.

I know when the big dogs put on ET-Streets to dyno on (like 15in wheel with 26in tire), with all that weight they give up a lot of power.......but they need it to stay on dyno.

How much do your fronts weigh? Maybe swap them to rear.

Tom

About 56lbs. Not a huge difference. My oem 18's with tires weighed 48lbs.

I figured that.

What EMS? How do your EGT's look? Reason I ask is that it sounds like timing is not what you think it is, combined with some major heatsoak.

Have you done a compression test or leak down test lately? If so, what were your numbers?

It not your wheels. your AIT's look perfect. timing is fairly aggressive.

if your car is mechanically sound, good compression/leakdown, then you just have a weak motor from the start, combined with an automatic transmission = lower than avg #'s

I'd say it could also be a miscalibrated dyno, but your trap times are awful as well.

367 on an auto is not unexpected at all

I'd ditch those headers as well - they aren't even properly sized for an NA motor, let alone an FI one

367whp is not too far off the mark We just tuned a 6sp G35 2.87 vortech car and made 428whp, he was running 20's and was tune on a 90 degree day. We have found that the Auto cars make about 10-12% less power then the 6sp cars...so when ya do the math its not too bad...

I'm using osiris. I don't have a pyrometer but my logs show timing, unless I can't trust what my logs are saying.

I'm planing on it by sunday.

I've been to two dynos and they both show the same. As for the traps...I was able to put 106mph on a weak as hell launch in a car that probably weighs about 3800lbs ( I have zero weight reduction in a fully loaded G + the vortech kit + the 20's + my 175lbs ) so I don't find them low for 349whp which is what I had before.

I wish there were more Vortech cars near me to be able to compare but they are all turbo. :(

What was the baseline on that G? My car put 240whp with testpipes and the plenum spacer so technically I gained 127whp. Was the gain similar?

those numbers sound on the low side of about right to me

If you guys owned the car, what would you do? I may do a compression check tomorrow...anything else?

your ebay replica exhaust isn't going to help you. you also needs some testpipes/downpipes. probably no need for headers, either. I would get a proper greddy evo2 and some aps 3" down farpipes.

What do u expect from an AT? Also u need to post your dyno with the boost level. I want to see when u are hitting 11psi and if it's really staying at 11psi at wot.

Also, check your blower to make sure its not taking a dump. U can always upgrade to a S trim for 500 more or T trim for 1300 more.

I have long tube headers and I ran an open dump so none of the above will help me.

I expect at least similar numbers to what other AT's have put down. I'll see if I can go to the dyno to get the graph, but no boost was logged. It does increase smoothly and hits 11psi at 6800rpm or so when I let go.

Last time I checked the blower inlet it looked fine, don't know about the impellers exducer though...I'd have to remove the blower to find out. I'd probably get a 928 impeller if it were screwed up though.

i would just drive the car and stop chasing #'s. Your tune sounds fine, your AIT's are fine, your setup seems fine.

You're right, but it really makes me wonder where the power is going because something HAS to be wrong to be so underpowered. But if all checks out then I can live with 360whp.:thumbup: